A compact plate-fin reformer (PFR) consisting of closely spaced plate-fins, in which endothermic and exothermic reactions take place in alternate chambers, has been studied. In the PFR, which was based on a plate-fin heat exchanger, catalytic combustion of the reforming gas, as a simulation of the fuel cell anode off gas (AOG), supplied the necessary heat for the reforming reaction. One reforming chamber, which was for hydrogen production, was integrated with two vaporization chambers and two combustion chambers to constitute a single unit of PFR. The PFR is very compact, easy to be placed and scaled up. The effect of the ratio of H2O/CH3OH on the performance of the PFR has been investigated, and temperature distributions in different chambers were studied. Besides, the stationary behavior of the PFR was also investigated. Heat transfer of the reformer was enhanced by internal plate-fins as well as by external catalytic combustion, which offer both high methanol conversion ratio and low CO concentration. In addition, the fully integrated reformer exhibited good test stability. Based on the PFR, a scale-up reformer was designed and operated continuously for 1000 h, with high methanol conversion ratio and low CO concentration. (c) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.